Managing data frames in switched networks

ABSTRACT

A routing device and a further routing device of a switched network form a virtual router and are addressable by a virtual Media Access Control (MAC) address. The further routing device receives at least one data frame and sends, to the routing device, a request instructing the routing device to send an alert message for conveying information about the virtual MAC address throughout the switched network.

RELATED APPLICATIONS

This application is a divisional of prior U.S. application Ser. No.15/519,663, filed 17 Apr. 2017, which was the National Stage ofInternational Application PCT/SE2014/051410 filed 26 Nov. 2014, theentire disclosure of each being hereby incorporated by reference herein.

TECHNICAL FIELD

Embodiments herein relate to communication systems, such as switchednetworks. In particular, a method and a routing device for managing dataframes as well as a method and a further routing device for managingdata frames are disclosed. Corresponding computer programs and carrierstherefor are also disclosed.

BACKGROUND

A communication system is sometimes conceptually described by an OpenSystems Interconnection model (OSI). The model partitions internalfunctions of the communication system into abstraction layers, such asphysical layer (layer 1), data link layer (layer 2), network layer(layer 3), transport layer (layer 4), etc.

An Ethernet network, as an example of a known communication system, isoften considered to be part of layer 2. The Ethernet network is also anexample of a so-called switched network, which uses only networkswitches rather than network hubs. The difference between networkswitches and hubs is that hubs forward data frames on all its ports atall times, while the network switches attempts to forward data framesonly on those ports that are relevant for a certain data frame.

The Ethernet network may carry a protocol called Virtual RouterRedundancy Protocol (VRRP), which is a known Internet Protocol. In otherexamples, the Ethernet network may carry Hot Standby Router Protocol(HSRP). The VRRP protocol provides automatic assignment of VRRP roles,routers in the Ethernet network. The VRRP roles include virtual routermaster and virtual router backup.

This kind of known Ethernet network may comprise multiple physicalrouters, which may be arranged and configured to represent a virtualrouter. The virtual router is assigned a VRRP MAC address. If thephysical router that is routing data frames on behalf of the virtualrouter fails—or a link connected to a port of the physical routerfails—, another physical router is selected automatically to replace it.A physical router that is receiving data frames addressed to the VRRPMAC address, e.g. at an interface of that physical router, has the roleof virtual router master.

The Ethernet network also comprises a number of network switches forforwarding data frames within the Ethernet network towards theirrespective destinations, such as the virtual router, i.e. a physicalrouter having the role of virtual router master. The data frames areMedia Access Control (MAC) data frames, which include a destination MACaddress field and a source MAC address field. See e.g. Institute ofElectrical and Electronics Engineers (IEEE) 802.3 specifications.

When a network switch receives a data frame, it looks up a destinationMAC address, located in the destination MAC address field of thereceived data frame, in a so called MAC address table in order to findout at which port of the network switch the received data frame shouldbe feed. Additionally, the networks switch checks the source addressfield of the received data frame and notes at which port the receiveddata frame was received.

When the MAC address in the source address field of the received dataframe is not present in the MAC address table of the switch, the sourceaddress field and the port, at which the data frame was received, is putinto the MAC address table for future use. It may also be the case thatthe MAC address in the source address field is mapped, according to theMAC address table, to another port. Then, the MAC address table needs tobe updated. This process of populating the MAC address table issometimes referred to as MAC learning.

Moreover, when the destination MAC address is not found in the MACaddress table, the network switch forwards the received data frame toall its ports, except for the port at which the data frame was received.This creates additional traffic, due to data frames being forwarded toadditional ports of the network switch, in the Ethernet network. Theadditional ports do not include the port at which the data frame wasreceived. When the data frames are received at a router, and the routercannot find its own MAC address in the destination MAC address field ofthe data frames, the router is said to be flooded. Accordingly, thenetwork switch is flooding data frames.

In an example, a host device, such as a Personal Computer or the like,sends data frames carrying payload data to the virtual router using theVRRP MAC address in the destination MAC address field. The virtualrouter is represented by a physical router that takes the role ofvirtual router master for a session identified by the VRRP MAC address.The session is typically a so called VRRP session which is known fromVRRP terminology. When the physical router sends data frames carryingpayload data back to the host, these data frames include a MAC addressof the physical router in the source MAC address field. The physicalrouter also sends special protocol frames, such as an announcementmessage according to VRRP i.e. an advertisement type message. Thesespecial protocol frames include the VRRP MAC address in the source MACaddress field. Typically, the announcement message is sent periodically,e.g. through broadcast or multicast.

A failure, such as that a network switch goes down, may happen in theEthernet network. A further switch, connected to the host device, willthen no longer be able to forward data frames, intended for the masterrouter, at the port connected to the network switch that went down.Thus, flooding will occur towards any other hosts or network switches,which are connected to the further switch mentioned above. See also FIG.1b below.

A problem is that flooding occurs for a long time in the Ethernetnetwork. The flooding will proceed until the announcement message isperiodically sent. In order to shorten the time during which floodingoccurs, the periodicity of the announcement message may be shortened.However, a shortened periodicity implies an increase of announcementmessages, which take up valuable network resources which otherwise couldbe used for data frame carrying payload data.

SUMMARY

An object may be to alleviate, or at least reduce, the above-mentionedproblem.

According to a first aspect, the object is achieved by a method,performed by a routing device of a switched network, for managing dataframes travelling in the Ethernet network. The routing device isaddressable by a virtual Media Access Control address, “MAC address”,for assignment to routers. The routing device sends a data framecomprising a source MAC address field, which includes a unicast MACaddress of the routing device. The routing device sends a messageincluding information about the virtual MAC address, wherein the routingdevice is configured to send, in a periodic manner, a periodic messagefor conveying information about the virtual MAC address throughout theswitched network.

According to a second aspect, the object is achieved by a routing deviceof a switched network. The routing device is configured to manage dataframes travelling in the Ethernet network. The routing device isaddressable by a virtual Media Access Control address, “MAC address”,for assignment to routers. The routing device is configured to send adata frame comprising a source MAC address field, which includes aunicast MAC address of the routing device. Hence, the routing device maysend data frames carrying payload data in a conventional manner.Furthermore, the routing device is configured to send a messageincluding information about the virtual MAC address. The routing deviceis configured to send, in a periodic manner, a periodic message forconveying information about the virtual MAC address throughout theswitched network.

According to a third aspect, the object is achieved by a method,performed by a further routing device of a switched network, formanaging data frames. The further routing device and a routing deviceare addressable by a virtual MAC address. The routing device and thefurther routing device form a virtual router. The further routing devicereceives at least one data frame. The further routing device sends, tothe routing device, a request instructing the routing device to send analert message for conveying information about the virtual MAC addressthroughout the switched network.

According to a fourth aspect, the object is achieved by a furtherrouting device of a switched network. The further routing device isconfigured to manage data frames. The further routing device and arouting device are addressable by a virtual MAC address. The routingdevice and the further routing device form a virtual router. The furtherrouting device is configured to receive at least one data frame.Furthermore, the further routing device is configured to send, to therouting device, a request instructing the routing device to send analert message for conveying information about the virtual MAC addressthroughout the switched network.

According to further aspects, the object is achieved by a computerprogram and a carrier for the computer program corresponding to theaspects above.

In some first embodiments, the message is a further data framecomprising a source MAC address field, which includes the virtual MACaddress. This means that different data frames, i.e. the data frame andthe further data frame, have source MAC address fields which contentsare different from each other. In more detail, the source MAC addressfield of the data frame includes the unicast MAC address of the routingdevice and the source MAC address field of the further data frameincludes the virtual MAC address. In this manner, the virtual MACaddress is used in the source MAC address field also for data frames,which e.g. includes payload data. This enables any existing networkswitches to learn the virtual MAC address from the further data frame,i.e. not only from special protocol frames as in prior art. Typically,data frames, such as the data frame and the further data frame, are sentmore frequent than the special protocol frames. Accordingly, time duringwhich flooding occurs is shortened.

In some second embodiments, the routing device receives, from a furtherrouting device, a request which instructs the routing device to send thealert message. The further routing device sends, preferably shortlyafter a failure or flooding at the further routing device, the request.In response to the request, the routing device sends the message, whichin these second embodiments comprises an alert message for conveyinginformation about the virtual MAC address throughout the switchednetwork. The alert message may be a special protocol frame, such as anannouncement message, in case of VRRP, i.e. an advertisement typemessage. By means of the alert message, the information about thevirtual MAC address is spread in the switched network. Hence, anyexisting network switch will learn the virtual MAC address and floodingmay cease. Thus, thanks to that the routing device sends the alertmessage in response to the request, time during which flooding occursmay be shortened.

An advantage is hence that load, e.g. in terms of superfluous dataframes caused by flooding, on the switched network is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The various aspects of embodiments disclosed herein, includingparticular features and advantages thereof, will be readily understoodfrom the following detailed description and the accompanying drawings.

FIGS. 1a and 1b are schematic overviews of an exemplifying switchednetwork in which embodiments herein may be implemented.

FIG. 2 is a schematic combined signaling and flowchart illustratingembodiments herein.

FIG. 3 is a flowchart illustrating embodiments of the method in therouting device.

FIG. 4 is a block diagram illustrating embodiments of the routingdevice.

FIG. 5 is a flowchart illustrating embodiments of the method in thefurther routing device.

FIG. 6 is a block diagram illustrating embodiments of the furtherrouting device.

DETAILED DESCRIPTION

Throughout the following description similar reference numerals havebeen used to denote similar features, such as nodes, actions, steps,modules, circuits, parts, items elements, units or the like, whenapplicable. In the Figures, features that appear in some embodiments areindicated by dashed lines.

FIG. 1a depicts an exemplifying communication system in whichembodiments herein may be implemented. In this example, thecommunication system is a switched network 100. In some examples, theswitched network 100 may be an Ethernet network, a Layer 2 network orthe like.

The switched network 100 comprises a routing device 110 and a furtherrouting device 120.

The routing device 110 and the further routing device 120 may bephysical routers for routing traffic, e.g. data frames, in a MediaAccess Control (MAC) layer, aka layer-2, of the switched network 100.Sometimes, this kind of physical router may be called a layer-3 switch(L3-switch). The routing devices 110, 120 terminate the layer-2 (L2) androutes information into layer-3 (L3).

The routing device 110 is addressable by a virtual Media Access Controladdress, “MAC address”, for assignment to routers. This may mean thatthe routing device 110 may handle a session, e.g. a VRRP session, forwhich an interface (not shown) of the routing device 110 acts as aso-called virtual router master according to VRRP technology or similartechnologies. The routing device 110 may of course handle more than onesession on the interface, but for sake of clarity only one session isconsidered. The session may be identified by the virtual MAC address,such as an VRRP MAC address.

In case the switched network 100 includes one or more virtual networks,such as Virtual Local Area Networks (VLANs), an identifier identifying asession, e.g. a VRRP session, in a first VLAN is required to be uniquewithin that VLAN. However, the same identifier may be used foridentifying another session, for example on the same routing device, ina second VLAN. The identifier may be a so called VRID for identifying avirtual router. The virtual MAC address may be generated from the VRID.In this manner, the session and/or the virtual router is communicativelyidentified by the VRRP MAC address in a unique manner per network, suchas a physical or virtual network. As used herein, the term “session” isused to denote that a virtual router is configured in the network. Thismeans that there is one session per virtual router.

The routing device 110 is configured to send, in a periodic manner, aperiodic message for conveying information about the virtual MAC addressthroughout the switched network 100. The information about the virtualMAC address may thus be conveyed, e.g. announced in the switched network100, by means of for example broadcast and/or multicast addressing,included in the periodic message. The routing device 110 may beconfigured to send the periodic message at points in time, which mayoccur at regular intervals. These periodic messages are sent in order toenable the network switches to learn the virtual MAC address.

The virtual MAC address may be a Virtual Router Redundancy ProtocolMedia Access Control address, “VRRP MAC address”, a VRRP Extended MACaddress, “VRRPE MAC Address”, a Hot Standby Router Protocol MAC Address“HSRP MAC address”, or a MAC Address according to a protocol forproviding virtual router functionality.

The periodic message may be an announcement message according to VRRP orVRRPE. The periodic message may have a different name in HSRP, but thesame function and/or purpose.

Also, the further routing device 120 is addressable by the virtual MACaddress. Consequently, the routing device 110 and the further routingdevice 120 form a virtual router 121, such as a VRRP router. The virtualrouter 121 is not a physical entity, but instead a virtual entitycomprising the routing device 110 and the further routing device 120.The virtual router 121 may include one or more additional routingdevices. It shall be noted that the virtual MAC address is a MAC addressapplicable for sending data frames to the virtual router 121, whicheffectively will be the routing device 110 or the further routing device120 depending on which interface acts as virtual router master for acertain VRRP session, again using terminology of VRRP or similarprotocols. It shall be understood that one and the same interface maytake different roles, such as virtual master router or virtual routerbackup, for different sessions in the routing device 110 and/or thefurther routing device 120.

According to the second embodiments, the further routing device 120manages no session on an interface towards the network switch 103. Thus,the interface acts as a virtual router backup with respect to thevirtual router master associated to the interface on the routing device110.

The switched network 100 further comprises a number of network switches101-105.

The switched network 100 further comprises a first host 130 and a secondhost 140. The first host 130 is addressable by a MAC address of thefirst host 130.

Traffic, e.g. data frames, between the first host 130 and the virtualrouter, i.e. the routing device, passes through network switches denotedby 101, 102 and 105.

It may here be said that the traffic may be sent to/from other hosts(not shown) via the virtual router 121. However, it shall be understoodthat the session is defined for reception of traffic, e.g. data frames,from the first host 130. In this manner, it is transparent to the firsthost 130, whether it is an interface of the routing device 110 or thefurther routing device 120 that currently acts as virtual router masterfor the session.

As used herein the term “host” may refer to a Personal Computer (PC), alaptop, a cellular phone, a tablet PC, a smartphone, a user equipment, aserver, a client, and the like.

In the Figure, each device, e.g. network switch, host, virtual routeretc., is assumed to have one port at each side. The solid arrowsindicate communication links to which ports are open and dashed arrowsindicate communication links to which ports are closed.

Now turning to FIG. 1 b, there is illustrated a scenario in which thenetwork switch 102 has a failure, e.g. power interruption, hardwaremalfunction, restart of network switch, failure of link to the networkswitch 102, manual blocking by configuration of ports or the like. Nowthat there is a failure, traffic needs to find a new way of passingbetween the first host 130 and the virtual router. The traffic may forexample pass through the network switches denoted by 101, 103, 104 and105.

When the failure has occurred, network switch 105 will flood, e.g.forward, any incoming data frames from the first host 130 to all itsports, except for the one towards the failed network switch 102. Forexample, the second host 140 will be flooded. Thanks to the firstembodiments, flooding at the second host 140 will cease rapidly.

Similarly, to the network switch 102, network switches 103, 104 willflood any incoming data frames. Thus, the further routing device 120will unexpectedly receive data frames, e.g. addressed to the routingdevice 110. That is to say, the further routing device 120 is flooded.Thanks to the second embodiments, flooding at the further routing device120 will cease rapidly.

FIG. 2 illustrates an exemplifying method according to embodimentsherein when performed in connection with the switched network 100 ofFIG. 1. The routing device 110 of the switched network 100 performs amethod for managing data frames, e.g. travelling in the switched network100. As mentioned, the data frames may be MAC data frames, Ethernetframes or similar.

With the second embodiments, mentioned in the summary section, thefurther routing device 120 of the switched network 100 performs a methodfor managing data frames.

The following actions may be performed in any suitable order.

Action 201

In the second embodiments, the further routing device 120 may beaddressable by the virtual MAC address, whereby the routing device 110and the further routing device 120 form the virtual router 121. Hence,the further routing device 120 may be ready to act as a virtual routermaster, but presently acts as virtual router backup. This means that thefurther routing device 120 takes the roles as described above for asession identified by the virtual MAC address. Needless to say, therouting device 120 may at the same time take the role of virtual routermaster for another session. The roles may apply for a certain interfaceof the routing device 120.

In this action according to the second embodiments, the further routingdevice 120 receives at least one data frame. The at least one data framemay be received at one or more ports of the further routing device 120.

Expressed differently, the further routing device 120 may detectflooding of the at least one data frame, where the at least one dataframe have a destination address field including the virtual MACaddress.

Action 202

In response to action 201, the further routing device 120 sends 202, tothe routing device 110, a request instructing the routing device 110 tosend an alert message for conveying information about the virtual MACaddress throughout the switched network 100. The alert message may be aspecial protocol frame, such as an announcement message, in case ofVRRP, i.e. an advertisement type message, a gratuitous-AddressResolution Protocol (grat-ARP) message or the like. ARP is used toconvert an Internet Protocol (IP) address to a physical address, such asan Ethernet address, also known as a MAC address.

The request may only be sent when the received at least one data framemay comprise a destination address field including the virtual MACaddress, as mentioned above.

In some examples, in order to avoid that action 202 is performedexcessively, i.e. much more than necessary, the request may only be sentless than a specific number of times counted from when action 201 wasperformed, i.e. flooding was detected at the further routing device.

Action 203

With the second embodiments, the routing device 110 may receive, fromthe further routing device 120, a request instructing the routing device110 to send the alert message.

Action 204

According to the first embodiments, the routing device 110 may manage alist comprising the unicast MAC address, the virtual MAC address as wellas further MAC addresses. In these embodiments, the message may be afurther data frame.

In first embodiments, the routing device 110 may thus, before action205, retrieve the unicast MAC address from the list.

In some examples, the routing device 110 may retrieve the unicast MACaddress according to an algorithm for handling the list. This means forexample that the routing device 110 applies a criterion, or thealgorithm, in order to select which address of the list to retrieve.

The algorithm may be a Round Robin algorithm, a First-In-First-Outalgorithm or the like.

Action 205

With the first and second embodiments, the routing device 110 sends,e.g. to the first host 130, the second host 140 or other hosts (notshown), a data frame comprising a source MAC address field, whichincludes a unicast MAC address of the routing device 110.

It shall be understood that the data frame may originate from said otherhosts (as mentioned, these other hosts are not shown). The other hostsmay thus send user data, carried by the data frame, to the first host130 or the second host 140.

In one example, the routing device 110 may even generate the data framecomprising the source MAC address field that includes the unicast MACaddress of the routing device 110. Such data frame may include a dummypayload, dummy user data, nonsense data or the like, i.e. any arbitrarydata that the routing device 110 may generate.

Action 206

In case the data frame comprises a destination address field, whichincludes the MAC address of the first host 130, the first host 130 mayreceive the data frame from the routing device 110 after the data framehas passed though the switched network 100, i.e. the network switches.

Action 207

The routing device 110 may, before action 208, retrieve the virtual MACaddress from the list. In some examples, the routing device 110 mayretrieve the virtual MAC address according to the algorithm.

Action 208

The routing device 110 sends a message including information about thevirtual MAC address. Thereby, enabling network switches 101-105 in theswitched network 100 to update their respective lists of MAC addresses,in which MAC addresses are mapped to ports of the respective networkswitch. The message may be different from the periodic message.

In the first embodiments, the message may be a further data framecomprising a source MAC address field, which may include, e.g. may bepopulated by, the virtual MAC address. In this manner, the messageenables the network switches 101, 102 and 105 to learn the virtual MACaddress.

The further data frame may comprise a destination address field, whichmay include the MAC address of the first host 130, the second host 140or other the like. Hence, as an example, the further data frame may besent to the first or second host 130, 140.

When action 208 is performed after the network switch 102 has went down,e.g. due to power failure, maintenance or the like, the network switch105 is able to learn the virtual MAC address by checking the sourceaddress field of the further data frame. Thus, when e.g. the first host130 sends data that should pass via the virtual router, the networkswitch 105 will not flood, e.g. at the second host, since the networkswitch has already registered with which port of the network switch 105the virtual MAC address is associated.

For example, flooding at the further routing device 120 may notnecessarily be interrupted, due to that the further data frame is sentas a unicast message to e.g. the first host 130. Therefore, depending onnetwork topology of the switched network 100, the further data frameneed not necessarily pass via the network switch 103, e.g. the networkswitch 101 may enable, or activate, a direct link (not shown) towardsthe network switch 101.

In a further embodiment, the message may comprise the virtual MACaddress, wherein a further source MAC address field of the data framemay include the message. This embodiment requires the data frames to beextended in terms of fields specified for the data frame, e.g. by meansof a change in a standard specification. In this manner, a data framemay be allowed to include multiple source MAC addresses in e.g. aplurality of source MAC address fields.

With the second embodiments, the message may comprise an alert messagefor conveying information about the virtual MAC address throughout theswitched network 100. In this manner, the message enables the networkswitches to learn the virtual MAC address. In particular, the networkswitch 103, which at least partly caused flooding at the further routingdevice 120 when the network switch 102 is down, is able to learn fromthe alert message with which port of the network switch 103 the virtualMAC address is associated.

In these embodiments, the alert message may be sent less than a specificnumber of times, or until one of the points in time may have beenreached. As mentioned above, the points in time relate to when theperiodic message is sent by the routing device 110.

Moreover, the alert message may be sent until said one of the points intime may have been reached since the routing device 110 received therequest in action 203.

Accordingly, action 208 may imply that the routing device 110 sends oneor more alert messages, e.g. one or more of the alert messages mentionedin the first sentence of this paragraph.

Action 209

When the destination address field of the further data frame includesthe MAC address of the first host 130, the first host 130 may receivethe message from the routing device 110.

Action 210

The routing device 110 may retrieve a present MAC address from the list.

In some examples, the routing device 110 may retrieve the present MACaddress according to the algorithm.

Action 211

The routing device 110 may send a present data frame comprising a sourceMAC address field, which may include the present MAC address.

In some particular embodiments, action 201, e.g. the detection of theflooding, may be performed by another device (not shown), which may bereferred to as a flooding detection device for detection of flooding ofdata frames in the switched network.

Furthermore, the flooding detection device may perform action 202. Inthis manner, the flooding detection, e.g. the function of floodingdetection, is put in an entity, i.e. the flooding detection device,which is separate from the routing devices 110, 120.

In FIG. 3, a schematic flowchart of exemplifying methods in the routingdevice 110 is shown. Again, the same reference numerals as above havebeen used to denote the same or similar features, in particular the samereference numerals have been used to denote the same or similar actions.Accordingly, the routing device 110 of the switched network 100 performsa method for managing data frames travelling in the switched network100.

As mentioned, the routing device 110 is addressable by a virtual MediaAccess Control address, “MAC address”, for assignment to routers. Therouting device 110 is configured to send, in a periodic manner, aperiodic message for conveying information about the virtual MAC addressthroughout the switched network 100. The routing device 110 may beconfigured to send the periodic message at points in time, which mayoccur with regular intervals. The virtual MAC address may be a VirtualRouter Redundancy Protocol Media Access Control address, “VRRP MACaddress”, a VRRP Extended MAC address, “VRRPE MAC Address”, a HotStandby Router Protocol MAC Address “HSRP MAC address”, or a MAC Addressaccording to a protocol for providing virtual router functionality. Theperiodic message may be an announcement message according to VRRP orVRRPE.

Again, with the second embodiments, the further routing device 120 maybe addressable by the virtual MAC address, whereby the routing device110 and the further routing device 120 forms a virtual router, whereinthe further routing device 120 may be ready to act as a master router.

The following actions may be performed in any suitable order.

Action 203

According to the second embodiments, the routing device 110 may receive,from the further routing device 120, a request instructing the routingdevice 110 to send the alert message.

Action 204

According to the first embodiments, the routing device 110 may manage alist comprising the unicast MAC address and the virtual MAC address,wherein the message may be a further data frame.

In that case, the routing device 110 may, before the sending 205 of thedata frame, retrieve the unicast MAC address from the list.

Action 205

Continuing with the first embodiments, the routing device 110 sends adata frame comprising a source MAC address field, which includes aunicast MAC address of the routing device 110.

The retrieving 205 of the unicast MAC address may be retrieved accordingto an algorithm for handling the list.

The algorithm may be a Round Robin algorithm, a First-In-First-Outalgorithm.

Action 207

The routing device 110 may, before the sending 208 of the further dataframe, retrieve 207 the virtual MAC address from the list. Theretrieving 207 of the virtual MAC address may be retrieved according tothe algorithm.

Action 208

The routing device 110 sends 208 a message including information aboutthe virtual MAC address. The message may be different from the periodicmessage.

In the first embodiments, the message may be a further data framecomprising a source MAC address field, which may include the virtual MACaddress.

The message may comprise the virtual MAC address, wherein a furthersource MAC address field of the data frame may include the message.

In the second embodiments, the message may comprise an alert message forconveying information about the virtual MAC address throughout theswitched network 100.

The sending 208 of the alert message may be performed less than aspecific number of times, or until one of the points in time may bereached.

The sending 208 of the alert message may be performed until said one ofthe points in time may be reached since the routing device 110 receivedthe request.

Action 210

The routing device 110 may retrieve a present MAC address from the list.The retrieving 210 of the present MAC address may be retrieved accordingto the algorithm.

Action 211

The routing device 110 may send a present data frame comprising a sourceMAC address field, which may include the present MAC address.

With reference to FIG. 4, a schematic block diagram of embodiments ofthe routing device 110 of FIG. 1 is shown. The routing device 110 of theswitched network 100 is thus configured to manage data frames travellingin the switched network 100.

As mentioned, the routing device 110 is addressable by a virtual MediaAccess Control address, “MAC address”, for assignment to routers.

The routing device 110 may comprise a processing module 401, such as ameans, one or more hardware modules and/or one or more software modulesfor performing the methods described herein.

The routing device 110 may further comprise a memory 402. The memory maycomprise, such as contain or store, a computer program 403.

According to some embodiments herein, the processing module 401comprises, e.g. ‘is embodied in the form of’ or ‘realized by’, aprocessing circuit 404 as an exemplifying hardware module. In theseembodiments, the memory 402 may comprise the computer program 403,comprising computer readable code units executable by the processingcircuit 404, whereby the routing device 110 is operative to perform themethods of FIG. 2 and/or FIG. 3.

In some other embodiments, the computer readable code units may causethe routing device 110 to perform the method according to FIG. 2 and/or3 when the computer readable code units are executed by the routingdevice 110.

FIG. 4 further illustrates a carrier 405, comprising the computerprogram 403 as described directly above. The carrier 405 may be one ofan electronic signal, an optical signal, a radio signal, and a computerreadable medium.

In some embodiments, the processing module 401 comprises an Input/Outputunit 406, which may be exemplified by a receiving module and/or asending module as described below when applicable.

In further embodiments, the processing module 401 may comprise one ormore of a sending module 410, a retrieving module 420, and a receivingmodule 430 as exemplifying hardware modules. In other examples, one ormore of the aforementioned exemplifying hardware modules may beimplemented as one or more software modules.

Therefore, according to the various embodiments described above, therouting device 110 is operative to and/or the routing device 110, theprocessing module 401 and/or the sending module 410 is configured tosend a data frame comprising a source MAC address field, which includesa unicast MAC address of the routing device 110. Furthermore, therouting device 110 is configured to send a message including informationabout the virtual MAC address, wherein the routing device 110 isconfigured to send, in a periodic manner, a periodic message forconveying information about the virtual MAC address throughout theswitched network 100.

The message may be different from the periodic message.

The routing device 110 may be configured to send the periodic message atpoints in time, which may occur with regular intervals.

The message may be a further data frame comprising a source MAC addressfield, which may include the virtual MAC address.

The message may comprise the virtual MAC address, wherein a furthersource MAC address field of the data frame may include the message.

In some embodiments, the routing device 110 may be configured to managea list comprising the unicast MAC address and the virtual MAC address,wherein the message may be the further data frame.

The routing device 110 may be operative to and/or the routing device110, the processing module 401 and/or the retrieving module 420 may beconfigured to, before sending of the data frame, retrieve the unicastMAC address from the list.

The routing device 110 may be operative to and/or the routing device110, the processing module 401 and/or the retrieving module 420, oranother retrieving module (not shown) may be configured to, beforesending of the further data frame, retrieve the virtual MAC address fromthe list.

Furthermore, the routing device 110 may be operative to and/or therouting device 110, the processing module 401 and/or the retrievingmodule 420, or a further retrieving module (not shown), may beconfigured to retrieve a present MAC address from the list.

Moreover, the routing device 110 may be operative to and/or the routingdevice 110, the processing module 401 and/or the sending module 410, oranother sending module (not shown), may be configured to send a presentdata frame comprising a source MAC address field, which may include thepresent MAC address.

The routing device 110 may be operative to and/or the routing device110, the processing module 401 and/or the retrieving module 420 may beconfigured to retrieve the unicast MAC address according to an algorithmfor handling the list. The routing device 110 may be operative to and/orthe routing device 110, the processing module 401 and/or the retrievingmodule 420 may be configured to retrieve the virtual MAC addressaccording to the algorithm. The routing device 110 may be operative toand/or the routing device 110, the processing module 401 and/or theretrieving module 420 may be configured to retrieve the present MACaddress according to the algorithm.

The algorithm may be a Round Robin algorithm, or a First-In-First-Outalgorithm.

The message may comprise an alert message for conveying informationabout the virtual MAC address throughout the switched network 100.

The routing device 110 may be operative to and/or the routing device110, the processing module 401 and/or the sending module 410 may beconfigured to send the alert message less than a specific number oftimes, or until one of the points in time may be reached.

In some further embodiments, a further routing device 120 may beaddressable by the virtual MAC address, whereby the routing device 110and the further routing device 120 forms a virtual router, wherein thefurther routing device 120 may be ready to act as a master router.

The routing device 110 may be operative to and/or the routing device110, the processing module 401 and/or the receiving module 430 may beconfigured to receive, from the further routing device 120, a requestinstructing the routing device 110 to send the alert message.

The routing device 110 may be operative to and/or the routing device110, the processing module 401 and/or the sending module 410 may beconfigured to send the alert message until said one of the points intime may be reached since the routing device 110 received the request.

As mentioned, the virtual MAC address may be a Virtual Router RedundancyProtocol Media Access Control address, “VRRP MAC address”, a VRRPExtended MAC address, “VRRPE MAC Address”, a Hot Standby Router ProtocolMAC Address “HSRP MAC address”, or a MAC Address according to a protocolfor providing virtual router functionality. The periodic message may bean announcement message according to VRRP or VRRPE.

In FIG. 5, a schematic flowchart of exemplifying methods in the furtherrouting device 120 is shown. Again, the same reference numerals as abovehave been used to denote the same or similar features, in particular thesame reference numerals have been used to denote the same or similaractions. Accordingly, the further routing device 120 of the switchednetwork 100 performs a method for managing data frames.

As mentioned, the further routing device 120 and a routing device 110are addressable by a virtual MAC address, wherein the routing device 110and the further routing device 120 form a virtual router.

The following actions, relating to the second embodiments, may beperformed in any suitable order.

Action 201

The further routing device 120 receives 201 at least one data frame.

Action 202

The further routing device 120 sends 202, to the routing device 110, arequest instructing the routing device 110 to send an alert message forconveying information about the virtual MAC address throughout theswitched network 100.

The sending 202 of the request may be only performed when the receiving201 of the at least one data frame may comprise detecting at least onedata frame comprising a destination address field including the virtualMAC address.

The sending 202 of the request may be performed less than a specificnumber of times counted from the detection 201 of flooding.

The receiving 201 of the at least one data frame may comprise receivingthe at least one data frame at one or more ports of the further routingdevice 120.

As mentioned, the virtual MAC address may be a Virtual Router RedundancyProtocol Media Access Control address, “VRRP MAC address”, a VRRPExtended MAC address, “VRRPE MAC Address”, a Hot Standby Router ProtocolMAC Address “HSRP MAC address”, or a MAC Address according to a protocolfor providing virtual router functionality. The periodic message may bean announcement message according to VRRP or VRRPE.

With reference to FIG. 6, a schematic block diagram of embodiments ofthe further routing device 120 of FIG. 1 is shown. The further routingdevice 120 of the switched network 100 is thus configured to manage dataframes

As mentioned, the further routing device 120 and a routing device 110are addressable by a virtual MAC address, wherein the routing device 110and the further routing device 120 form a virtual router.

The further routing device 120 may comprise a processing module 601,such as a means, one or more hardware modules and/or one or moresoftware modules for performing the methods described herein.

The further routing device 120 may further comprise a memory 602. Thememory may comprise, such as contain or store, a computer program 603.

According to some embodiments herein, the processing module 601comprises, e.g. ‘is embodied in the form of’ or ‘realized by’, aprocessing circuit 604 as an exemplifying hardware module. In theseembodiments, the memory 602 may comprise the computer program 603,comprising computer readable code units executable by the processingcircuit 604, whereby the further routing device 120 is operative toperform the methods of FIG. 2 and/or FIG. 5.

In some other embodiments, the computer readable code units may causethe further routing device 120 to perform the method according to FIG. 2and/or 5 when the computer readable code units are executed by thefurther routing device 120.

FIG. 6 further illustrates a carrier 605, comprising the computerprogram 603 as described directly above. The carrier 605 may be one ofan electronic signal, an optical signal, a radio signal, and a computerreadable medium.

In some embodiments, the processing module 601 comprises an Input/Outputunit 606, which may be exemplified by a receiving module and/or asending module as described below when applicable.

In further embodiments, the processing module 601 may comprise one ormore of a receiving module 610, and a sending module 620 as exemplifyinghardware modules. In other examples, one or more of the aforementionedexemplifying hardware modules may be implemented as one or more softwaremodules.

Therefore, according to the various embodiments described above, thefurther routing device 120 is operative to and/or the further routingdevice 120, the processing module 601 and/or the receiving module 610 isconfigured to receive at least one data frame.

The further routing device 120 may be operative to and/or the furtherrouting device 120, the processing module 601 and/or the receivingmodule 610 may be configured to receive the at least one data frame atone or more ports of the further routing device 120.

Furthermore, the further routing device 120 is operative to and/or thefurther routing device 120, the processing module 601 and/or the sendingmodule 620 is configured to send, to the routing device 110, a requestinstructing the routing device 110 to send an alert message forconveying information about the virtual MAC address throughout theswitched network 100.

The further routing device 120 may be operative to and/or the furtherrouting device 120, the processing module 601 and/or the sending module620 may be configured to send the request only when the received atleast one data frame may comprise a destination address field includingthe virtual MAC address.

The further routing device 120 may be operative to and/or the furtherrouting device 120, the processing module 601 and/or the sending module620 may be configured to send the request less than a specific number oftimes counted from when the at least one data frame was received.

As mentioned, the virtual MAC address may be a Virtual Router RedundancyProtocol Media Access Control address, “VRRP MAC address”, a VRRPExtended MAC address, “VRRPE MAC Address”, a Hot Standby Router ProtocolMAC Address “HSRP MAC address”, or a MAC Address according to a protocolfor providing virtual router functionality. The periodic message may bean announcement message according to VRRP or VRRPE.

As used herein, the term “processing module” may include one or morehardware modules, one or more software modules or a combination thereof.Any such module, be it a hardware, software or a combinedhardware-software module, may be a determining means, estimating means,capturing means, associating means, comparing means, identificationmeans, selecting means, receiving means, sending means or the like asdisclosed herein. As an example, the expression “means” may be a modulecorresponding to the modules listed above in conjunction with theFigures.

As used herein, the term “processing circuit” may refer to a processingunit, a processor, an Application Specific integrated Circuit (ASIC), aField-Programmable Gate Array (FPGA) or the like. The processing circuitor the like may comprise one or more processor kernels.

As used herein, the expression “configured to” may mean that aprocessing circuit is configured to, or adapted to, by means of softwareconfiguration and/or hardware configuration, perform one or more of theactions described herein.

As used herein, the expressions “acting as virtual router master” and/or“acting as virtual router backup” may be used interchangeably with theexpressions “take the role of virtual router master” and/or “take therole of virtual router backup” while implying a similar or the samemeaning.

As used herein, the term “memory” may refer to a hard disk, a magneticstorage medium, a portable computer diskette or disc, flash memory,random access memory (RAM) or the like. Furthermore, the term “memory”may refer to an internal register memory of a processor or the like.

As used herein, the term “computer readable medium” may be a UniversalSerial Bus (USB) memory, a DVD-disc, a Blu-ray disc, a software modulethat is received as a stream of data, a Flash memory, a hard drive, amemory card, such as a MemoryStick, a Multimedia Card (MMC), etc.

As used herein, the term “computer readable code units” may be text of acomputer program, parts of or an entire binary file representing acomputer program in a compiled format or anything there between.

As used herein, the term “radio resource” may refer to a certain codingof a signal and/or a time frame and/or a frequency range in which thesignal is transmitted. In some examples, a resource may refer to one ormore Physical Resource Blocks (PRB) which is used when transmitting thesignal. In more detail, a PRB may be in the form of Orthogonal FrequencyDivision Multiplexing (OFDM) PHY resource blocks (PRB). The term“physical resource block” is known from 3GPP terminology relating toe.g. Long Term Evolution Systems.

As used herein, the terms “number” and/or “value” may be any kind ofdigit, such as binary, real, imaginary, or rational number or the like.Moreover, “number” and/or “value” may be one or more characters, such asa letter or a string of letters. “Number” and/or “value” may also berepresented by a bit string.

As used herein, the expression “in some embodiments” has been used toindicate that the features of the embodiment described may be combinedwith any other embodiment disclosed herein.

Even though embodiments of the various aspects have been described, manydifferent alterations, modifications and the like thereof will becomeapparent for those skilled in the art. The described embodiments aretherefore not intended to limit the scope of the present disclosure.

What is claimed is:
 1. A method of managing data frames, performed by afurther routing device of a switched network, the method comprising:receiving at least one data frame; and sending, to a routing device, arequest instructing the routing device to send an alert message forconveying information about a virtual MAC address throughout theswitched network, wherein the routing device and further routing deviceform a virtual router and are addressable by the virtual MAC address;wherein the virtual MAC address is a Virtual Router Redundancy Protocol(VRRP) Media Access Control address, a VRRP Extended MAC address, or aHot Standby Router Protocol MAC Address.
 2. The method of claim 1,wherein the sending of the request is only performed when the receivingof the at least one data frame comprises detecting at least one dataframe comprising a destination address field including the virtual MACaddress.
 3. The method of claim 2, wherein the sending of the request isperformed less than a specific number of times counted from detection offlooding.
 4. The method of claim 1, wherein the receiving of the atleast one data frame comprises receiving the at least one data frame atone or more ports of the further routing device.
 5. A further routingdevice of a switched network, the further routing device comprising:processing circuitry; memory containing instructions executable by theprocessing circuitry to configure the further routing device to: receiveat least one data frame; and send, to a routing device, a requestinstructing the routing device to send an alert message for conveyinginformation about a virtual MAC address throughout the switched network,wherein the routing device and further routing device form a virtualrouter and are addressable by the virtual MAC address; wherein thevirtual MAC address is a Virtual Router Redundancy Protocol (VRRP) MediaAccess Control address, a VRRP Extended MAC address, or a Hot StandbyRouter Protocol MAC Address.
 6. The further routing device of claim 5,wherein the instructions are such that the further routing device isoperative to send the request only when the received at least one dataframe comprises a destination address field including the virtual MACaddress.
 7. The further routing device of claim 6, wherein theinstructions are such that the further routing device is operative tosend the request less than a specific number of times counted from whenthe at least one data frame was received.
 8. The further routing deviceof claim 5, wherein the instructions are such that the further routingdevice is operative to receive the at least one data frame at one ormore ports of the further routing device.
 9. A non-transitory computerreadable medium storing a computer program product for managing dataframes, the computer program product comprising software instructionswhich, when run on processing circuitry of a further routing device of aswitched network, causes the further routing device to: receive at leastone data frame; and send, to a routing device, a request instructing therouting device to send an alert message for conveying information abouta virtual MAC address through the switched network, wherein the routingdevice and further routing device form a virtual router and areaddressable by the virtual MAC address; wherein the virtual MAC addressis a Virtual Router Redundancy Protocol (VRRP) Media Access Controladdress, a VRRP Extended MAC address, or a Hot Standby Router ProtocolMAC Address.
 10. The non-transitory computer readable medium of claim 9,wherein the instructions further cause the further routing device tosend the request only when the received at least one data framecomprises a destination address field including the virtual MAC address.11. The non-transitory computer readable medium of claim 10, wherein theinstructions further cause the further routing device to send therequest less than a specific number of times counted from when the atleast one data frame was received.
 12. The non-transitory computerreadable medium of claim 9, wherein the instructions further cause thefurther routing device to receive the at least one data frame at one ormore ports of the further routing device.
 13. A method of managing dataframes, performed by a further routing device of a switched network, themethod comprising: receiving at least one data frame; and sending, to arouting device, a request instructing the routing device to send analert message for conveying information about a virtual MAC addressthroughout the switched network: only when the receiving of the at leastone data frame comprises detecting at least one data frame comprising adestination address field including the virtual MAC address; and lessthan a specific number of times counted from detection of flooding;wherein the routing device and further routing device form a virtualrouter and are addressable by the virtual MAC address.
 14. The method ofclaim 13, wherein the receiving of the at least one data frame comprisesreceiving the at least one data frame at one or more ports of thefurther routing device.
 15. A further routing device of a switchednetwork, the further routing device comprising: processing circuitry;memory containing instructions executable by the processing circuitry toconfigure the further routing device to: receive at least one dataframe; and send, to a routing device, a request instructing the routingdevice to send an alert message for conveying information about avirtual MAC address throughout the switched network: only when thereceived at least one data frame comprises a destination address fieldincluding the virtual MAC address; and less than a specific number oftimes counted from when the at least one data frame was received;wherein the routing device and further routing device form a virtualrouter and are addressable by the virtual MAC address.
 16. The furtherrouting device of claim 15, wherein the instructions are such that thefurther routing device is operative to receive the at least one dataframe at one or more ports of the further routing device.
 17. Anon-transitory computer readable medium storing a computer programproduct for managing data frames, the computer program productcomprising software instructions which, when run on processing circuitryof a further routing device of a switched network, causes the furtherrouting device to: receive at least one data frame; and send, to arouting device, a request instructing the routing device to send analert message for conveying information about a virtual MAC addressthrough the switched network only when the received at least one dataframe comprises a destination address field including the virtual MACaddress: only when the received at least one data frame comprises adestination address field including the virtual MAC address; and lessthan a specific number of times counted from when the at least one dataframe was received; wherein the routing device and further routingdevice form a virtual router and are addressable by the virtual MACaddress.
 18. The non-transitory computer readable medium of claim 17,wherein the instructions further cause the further routing device toreceive the at least one data frame at one or more ports of the furtherrouting device.